| Summary: | We propose and investigate the intrinsically thinnest transistor concept: a monolayer ballistic heterojunction bipolar transistor based on a lateral heterostructure of transition metal dichalcogenides. The device is intrinsically thinner than a field effect transistor because it does not need a top or bottom gate, since transport is controlled by the electrochemical potential of the base electrode. As is typical of bipolar transistors, the collector current undergoes a tenfold increase for each 60 mV increase of the base voltage over several orders of magnitude at room temperature, without sophisticated optimization of the electrostatics. We present a detailed investigation based on self-consistent simulations of electrostatics and quantum transport for both electrons and holes of a p-n-p device using MoS_{2} for the 10-nm base and WSe_{2} for the emitter and collector. Our three-terminal device simulations confirm the working principle and a large current modulation I_{ON}/I_{OFF}∼10^{8} for ΔV_{EB}=0.5V. Assuming ballistic transport, we are able to achieve a current gain β∼10^{4} over several orders of magnitude of collector current and a cutoff frequency up to the THz range. The exploration of the rich world of bipolar nanoscale device concepts in two-dimensional materials is promising for their potential applications in electronics and optoelectronics.
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